Brown & Sharpe 618 Micromaster VFD / Phase Converter

Just acquired one of these lovely machines, although it is not in my possession yet. In preparation for its arrival, I want to figure out my power situation. Its wired 240V but I am still rockin' single phase. IIRC, some of the motors on this are single phase tho, right? So, my question is, which motors are single and which are three phase? I think this will dictate whether I go with a VFD or a static phase converter. Thanks

Is it automatic or manual?

All the motors are 3 phase unless it has an aftermarket coolant pump.

Smrtman5 said:

Just acquired one of these lovely machines, although it is not in my possession yet. In preparation for its arrival, I want to figure out my power situation. Its wired 240V but I am still rockin' single phase. IIRC, some of the motors on this are single phase tho, right? So, my question is, which motors are single and which are three phase? I think this will dictate whether I go with a VFD or a static phase converter. Thanks

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"Static" Phase Converter is an oxymoron. You do NOT want one around a surface grinder!

A DECENT RPC will run the whole shebang, and will not stress stone-age motor windings nor flute expensive bearings with fast switching transients.

Next-best choice might be a good grade of VFD, sized only for the spindle drive motor, and also blessed with a load side dy/dt or even "pure sine wave" filter inductor. ANy good VFD will have specs for what it wants right in the manual - no need of DIY kludging.

Then a small RPC to pick-up all other 3-Phase loads in a single go.

I'd just cheat and run it off one of my two 10 HP Phase-Perfects, but then.. for a time, I had more money than good economic sense. No pressing need for you to duplicate THAT costly side-trip, so

..RPC time? Good items to have under-roof, anyway.

2CW

ewlsey said:

Is it automatic or manual?

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Cross feed only, no downfeed.

thermite said:

nor flute expensive bearings with fast switching transients.

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Is that where those AEGIS rings come in?

thermite said:

and also blessed with a load side dy/dt or even "pure sine wave" filter inductor.

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Can you elaborate on the benefits of this a bit?

I probably should buy a RPC...if the budget didnt go towards the grinder!

Smrtman5 said:

Is that where those AEGIS rings come in?

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Helwig Carbon - the "old line" brush maker - are one of several who have bolt-on solutions. Check it out online. Also tons of "white papers" out there, many with specialty camera photos of corona in action and bearings that have been damaged.

Machine-tool precision spindle bearings - SG's high on the list - should NOT be so casually treated. Too DAMNED expensive to replace, basically.

For the cost, methinks it make far more sense to stay with pure-sine wave power sources to begin with, rather than monkey-patch older motors around modern VFD's rudeness.

Now.. any RPC so qualifies.

It offers-up a certain amount of rude behaviour UP the line - utility-(local)-grid-side (see "THD", and how it might annoy your nearest residential neigbour on the same pole-pig or ground-vault transformer..).

Even so, any RPC's OUTPUT, or load, side is pure sine-wave, never, ever any fast-switching, fast-rise transients. So..even if.. one leg is not as 'stiff' as the other two, all that means to a 3-Phase motor as load is that it can only hit a max of 91% or so of "nameplate'.

For most of our use? "Bee Eff Dee". RPC's JFW.

I probably should buy a RPC...if the budget didnt go towards the grinder!

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Two 10 HP Phase-perfects (one old "blue" bought used, one brand-new "white") and my more beloved of machines Dee Cee drive as well?

I still run a 10 HP RPC too! "Bullet proof" in way, they are.

"Half" home-built.

I bought a brand-new Weg (Brasil, not China) 10 HP 1750 RPM 3-Phase motor, under $400 shipped, and then - only AFTER I KNEW the RPM I'd be working with - ordered one of Jim's "Phase-Craft" - which is also his PM handle - RPC starter/Control boxes. I know how to build my own. I even have all the needed parts to build several.

I have better things to do with my scarce time that try to catch-up to what Jim already knows - even just as to the "nuisance" diversion of DIY'ing or adapting a bleepin' enclosure, cutting and terminating wire, and mounting the darned parts!

Plenty of OTHER stuff I just HAVE TO "DIY", so... made more economic sense than might first appear to just go near-as-dammit "turnkey" on a mission-critical item of this sort.

An SG needs clean and very stable power. Take note, for example, that 1-P driven ones are notorious for fine "watermark" patterns on the ground surface from the ever-so-slight vibration at the wheel.

OTOH - SG's do not, hardly ever - mind the 9% or 10% drop from theoretical max HP of RPC vs "true" utility mains nor 4 LARGE-plus cost of a new Phase-Perfect.

And.. an RPC can drive all sorts of OTHER 3-Phase goods without the "reprogramming" recommended if one tries to use a VFD for more than a single matched and dedicated motor load.

RPC also last near-as-dammit forever, vs a VFD wanting replaced every several years because the new caps any reputable maker specs - right in the manual, read it and weep - usually cost more than a whole new VFD.

3CW

There are 2ea 3ph motors in the post ww2 versions - 1 for the auto table feeds & one in the cartridge spindle. Some of the older belt drive spindles may have run everything off one motor and belts, I'm not sure.

my 618, rescraped here. has been running almost a couple decades on the typical $-0- shop brew RPC.

1200 rpm 5HP GE motor in the corner with a flywheel it came with (looks like a 10" faceplate with about a 3" spigot on the motor shaft). I wrap a pull rope around the spigot, pull steadily as i straighten up, finishing with a snap, reaching on up in the joists where the disconnect is mounted, flipping it to -on-. This runs the metal shop, including a 220 to 440V transformer for the higher volt machines. The transformer was already mounted, hanging off the back of the DoALL 1030 grinder; but now feeds other machines in addition.

My primary business is the wood shop. That has a (free) 7.5HP idler started with a static convertor, which is immediately cut back out of the line. That rotary then has a small device box of run capacitors I used to balance it, and the output goes to a surplus 3ph panel box my lineman neighbor gave me. From there is is distributed just like power out of any load center.

smt

Smrtman5 said:

Cross feed only, no downfeed.




Is that where those AEGIS rings come in?

Can you elaborate on the benefits of this a bit?

I probably should buy a RPC...if the budget didnt go towards the grinder!

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Let me take a stab at this. Hopefully I won't get too far off track.

Bearing fluting and crosstalk can be an issue with VFDs but is usually not a problem on our machines.

AEGIS - all I will say is that I tested a 1 hp motor at 240 volts. I artificially pushed high current (high frequency from the VFD)through the bearings. Ran the tests for 90 days. AEGIS ring showed fluting in both bearings but not catastrophic. Helwig high metal carbon brush no damage in the bearings after 90 days. Without any ground brushes, catastrophic bearing failure in 70 hours. So AEGIS brush did help, but there are concerns if it stays effective long-term.

In our machines, it would surprise me that we would be dealing with bearing fluting from VFDs, but some of the larger (10, 20 30 hp) certainly fall into the susceptible category. The smaller ones can also get hit, but less likely.

So what causes electrical bearing fluting? There are 3 causes:

1. Circulating currents caused by magnetic dissimetry and distributed capacitance between the stator windings and the rotor. Solution is to insulate opposite drive end bearing with at least 25 ohms at 10 mhz impedance (my recommendation). Have not seen any documented cases of this type of failure in the motor hp ranges we use. Tend to be at 200 hp and up.

2. Stator to frame capacitance currents. Can be very harmful in our machines. Solution is to use a properly shielded motor lead cable properly bonded at both ends of the motor and drive. The shield acts like a low impedance return path for the high frequency currents. Conventional ground wires are ineffective at these frequencies. Metallic conduit and metallic sealtite is also somewhat effective.

3. Stator to rotor capacitive currents. Much lower capacitance than stator to frame capacitance but for some reason smaller motors (10 - 50 hp) seem to be affected and then the larger ones not as much until to get to several hundred horsepower. This is where the HVAC industry got hit and where the AEGIS has earned its name. The solution is a ground brush on the drive end of the motor.

All of these currents can be identified using an oscilloscope (voltage) and a Rogowski coil (current).

I am actually in the process of co-authoring an IEEE paper on ground brush effectiveness.

Sorry if I got too technical - I get carried away very easily.

markz528 said:

Let me take a stab at this. Hopefully I won't get too far off track.

Bearing fluting and crosstalk can be an issue with VFDs but is usually not a problem on our machines.

AEGIS - all I will say is that I tested a 1 hp motor at 240 volts. I artificially pushed high current (high frequency from the VFD)through the bearings. Ran the tests for 90 days. AEGIS ring showed fluting in both bearings but not catastrophic. Helwig high metal carbon brush no damage in the bearings after 90 days. Without any ground brushes, catastrophic bearing failure in 70 hours. So AEGIS brush did help, but there are concerns if it stays effective long-term.

In our machines, it would surprise me that we would be dealing with bearing fluting from VFDs, but some of the larger (10, 20 30 hp) certainly fall into the susceptible category. The smaller ones can also get hit, but less likely.

So what causes electrical bearing fluting? There are 3 causes:

1. Circulating currents caused by magnetic dissimetry and distributed capacitance between the stator windings and the rotor. Solution is to insulate opposite drive end bearing with at least 25 ohms at 10 mhz impedance (my recommendation). Have not seen any documented cases of this type of failure in the motor hp ranges we use. Tend to be at 200 hp and up.

2. Stator to frame capacitance currents. Can be very harmful in our machines. Solution is to use a properly shielded motor lead cable properly bonded at both ends of the motor and drive. The shield acts like a low impedance return path for the high frequency currents. Conventional ground wires are ineffective at these frequencies. Metallic conduit and metallic sealtite is also somewhat effective.

3. Stator to rotor capacitive currents. Much lower capacitance than stator to frame capacitance but for some reason smaller motors (10 - 50 hp) seem to be affected and then the larger ones not as much until to get to several hundred horsepower. This is where the HVAC industry got hit and where the AEGIS has earned its name. The solution is a ground brush on the drive end of the motor.

All of these currents can be identified using an oscilloscope (voltage) and a Rogowski coil (current).

I am actually in the process of co-authoring an IEEE paper on ground brush effectiveness.

Sorry if I got too technical - I get carried away very easily.

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Thank you, thank you, thank you!

There are rather a lot of very good metal-manglers - bright folks- who just never had to deal with these issues. Unfortunately, they seem to "brush it off" (pun intended) mentally, rather than physically, and believe any possible risk in VFD use to be an Old Wive's tale.

Well.. old "site bonding and grounding" for telco facilities, Technical Writer (Northrop-Page) and implementor (Cable & Wireless pensioner..) Old Husband, not wife, in my case!



But then again...I/we (lloooooong ago IEEEE member..) did take the time to research and READ.

Good luck with your "white paper". Surely hope it gets paid more attention to than has too often been the case with other ones!

The problem needs to be sorted AT THE SOURCE - before power leads depart the VFD.

Some few do. All should do.


Regards,

Bill

markz528 said:

AEGIS - all I will say is that I tested a 1 hp motor at 240 volts. I artificially pushed high current (high frequency from the VFD)through the bearings. Ran the tests for 90 days. AEGIS ring showed fluting in both bearings but not catastrophic. Helwig high metal carbon brush no damage in the bearings after 90 days. Without any ground brushes, catastrophic bearing failure in 70 hours. So AEGIS brush did help, but there are concerns if it stays effective long-term.

...

I am actually in the process of co-authoring an IEEE paper on ground brush effectiveness.

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I'm surprised to hear you saw fluting with AEGIS. Could you provide more detail on these experiments? ...or will we have to wait for the finished paper?

markz528 said:

Solution is to insulate opposite drive end bearing with at least 25 ohms at 10 mhz impedance (my recommendation).

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I am curious: why does impedance at 0.01 Hz matter? I would have expected the relevant frequencies to be either 60 Hz or the chopping frequency of the VFD.

All of these currents can be identified using an oscilloscope (voltage) and a Rogowski coil (current).

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I would like to learn the procedure to do this. Since the damage is incremental over time, it would be nice to be able to test a new motor/VFD combination to see if the bearings are being damaged.

I am actually in the process of co-authoring an IEEE paper on ground brush effectiveness.

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Please post a DOI or link when it's available!

ballen said:

I am curious: why does impedance at 0.01 Hz matter? I would have expected the relevant frequencies to be either 60 Hz or the chopping frequency of the VFD.

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10 MEGA Hz is easier to measure than guessing at the VFD's artifact rise-times. And it is 1 BILLION times the rate of the ".01 Hz" you cited. Ye've mentally moved the decimal point the wrong direction!

Please post a DOI or link when it's available!

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Keep in mind that IEEE funds a part of its existence by CHARGING for things they publish. Main reason I held a membership years ago.

Quality work, IEEE usually has, but so much of a b***dy nuisance to GET it many professionals figure what goes into IEEE doesn't easily come back OUT, so just give it all a miss and settle for alternative sources.

Manufacturers of goods are at the head of that list. Most give away their "white paper" work for free as .pdf downloads to enhance credibility, helpfullness, improve support, reduce f**k-ups, and eventually improve their sales and longevity.

Yaskawa/Magnetek and latter-day market majors have free pubs as can educate a person on VFD's. Reliance legacy pubs do much the same for Dee Cee motors and & drives. etc, etc...

IEEE has no "product" aside from pubs and standards-input, doesn't really have a low-level "death wish", just fewer options for funding.

thermite said:

10 MEGA Hz is easier to measure

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The OP wrote "mhz". "m" is the abbreviation for "milli" = 0.001. The abbreviation for "mega" = 1,000,000 is "M". But if the OP meant "MHz" as you suggest, then it makes sense because typical chopping frequencies are tens of kHz.

Keep in mind that IEEE funds a part of its existence by CHARGING for things they publish.

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I'm a Fellow of the IEEE, so it's not a problem for me.

ballen said:

The OP wrote "mhz". "m" is the abbreviation for "milli" = 0.001. The abbreviation for "mega" = 1,000,000 is "M". But if the OP meant "MHz" as you suggest, then it makes sense because typical chopping frequencies are tens of kHz.



I'm a Fellow of the IEEE, so it's not a problem for me.

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Surely it IS a "problem" when you invent text not even present to justify what was not said to begin with.

The OP did indeed write MEGA Herz.

It was a "Fellow of the IEEE" - or so claimeth he - that could not grok that and wrote, and I AGAIN quote:

impedance at 0.01 Hz

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EG: There WAS NO "m" OR "M", just bare-nekked ".01 Hz" in YOUR post.

It isn't the "OP" or his post who needs explaining.

It's the slow-clocking, fast-talking "point-zero-one" fellah who is the puzzler.

thermite said:

The OP did indeed write MEGA Herz.

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I was referring to post #7 in this thread, where markz528 wrote, "Solution is to insulate opposite drive end bearing with at least 25 ohms at 10 mhz impedance (my recommendation)." 10 mHz = 10 milli-Herz = 0.01 Hz, which is confusing to me. I agree that markz528 may have meant 10 MHz = 10 Megaherz = 10,000,000 Hz. Why not wait a bit and let markz528 reply?

ballen said:

I was referring to post #7 in this thread, where markz528 wrote, "Solution is to insulate opposite drive end bearing with at least 25 ohms at 10 mhz impedance (my recommendation)." 10 mHz = 10 milli-Herz = 0.01 Hz, which is confusing to me. I agree that markz528 may have meant 10 MHz = 10 Megaherz = 10,000,000 Hz. Why not wait a bit and let markz528 reply?

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Wait for WHAT?

Mark never set a foot wrong to begin with!

YOU are the sole and ONLY "0.01 Hertz" contributor, confuser, bamboozler, apologist, rationalizer, side-tracker!!!


Grow a pair instead of trying to BORROW a pair or blame the bystanders - and just 'fess up - it is all IN PRINT, so there ain't no place to HIDE!

Simple mistake now being turned into an(other) example of creeping senility as with alfin brake ignorance and BFBI Deckel riser projects? Or just WHAT?

Thanks all for the input. I am only tangentially familiar with these concepts and more used to applying VFDs to off-the-shelf motors of small HP and frankly, little value (compared to machine tools & machine tool bearings). Just to clarify, are the phenomena described here reserved for the motor bearings or can it propagate throughout the machine and affect any of the machine bearings?

Smrtman5 said:

Just to clarify, are the phenomena described here reserved for the motor bearings or can it propagate throughout the machine and affect any of the machine bearings?

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In fact, not theory, no radiated energy anywhere WE can stay alive and comfortable is ever quite 100% blocked - it is just "attenuated" to greater and greater degrees until we think it is.

Also in fact, no, the effects won't escape the motor being powered EXCEPT AS rude noises that your WiFi can handle by re-sending packets, but a TV, radio, or stereo sound system may bitch about.

Or not.

"DOTS" (Depends On The Situation) and "PUNY" (Probably, Usually, Normally, Generally) both apply.

Yup - should of wrote MHz. I tend to make that error a lot as I get lazy when I type. The 25 ohms is at 10,000,000 HZ.

As far as the AEGIS, in my testing I purposely pushed high current through it. If memory serves me right, it was in the 12 - 13 amps (peak to peak) at over 1 MHz. So the AEGIS certainly helped when you consider that 70 hours was all it took to catastrophically fail the bearings with no protection. In real world applications, the current will be substantially lower than in my testing.

I will put something together to discuss more about what causes the fluting, how to prevent it in our machines and how to test for it. It will take me a few days to put it together.............

markz528 said:

Yup - should of wrote MHz. I tend to make that error a lot as I get lazy when I type. The 25 ohms is at 10,000,000 HZ.

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OK, thanks for clarifying this.

I will put something together to discuss more about what causes the fluting, how to prevent it in our machines and how to test for it.

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Thanks. As I wrote earlier, I am especially interested in the test procedure, because it would be nice to be able to test a motor/VFD combination to see if the bearings are being damaged. I have never heard of a Rogowski coil before!

thermite said:

Also in fact, no, the effects won't escape the motor being powered EXCEPT AS rude noises that your WiFi can handle by re-sending packets, but a TV, radio, or stereo sound system may bitch about.

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The spindle motor drives the spindle via belts, in this situation if I understand correctly, stray currents in the spindle bearings would not be a major issue. However, I could imagine some unwanted vibration traveling from the motor through the machine, resulting in a subpar surface finish.

My current plan is for a small RPC, but I just want to understand the situation fully.